The subject matter described herein relates to surface inspection techniques, and more particularly to surface scanning, for materials such as, for example, semiconductor materials.
When a patterned wafer is illuminated, the intensity of scattered and reflected light is dependent on the orientation of the incoming radiation with respect to the pattern. Thus, a spiral scan of a patterned wafer will have variations in image intensity as a function of azimuthal angle (as measured from the center of the wafer). The intensity variations complicate the algorithms required to extricate defect information from the image and can dramatically reduce the sensitivity to a variety of defect types. Other modes of surface scanning may be useful for reducing these artifacts.